1. Field of the Invention
The present invention relates to an improvement of an emulsified composition, particularly to an emulsified composition utilized as a preparation for a parenteral administration.
2. Description of the Related Art
Various emulsified compositions are used in the fields of, for example, pharmaceuticals and quasi-drugs, and as such an emulsified composition, a fat emulsion for an intravenous injection comprising lipid spheres with an average particle size of about 0.2 .mu.m dispersed in an aqueous phase, is known in the art. This composition is generally obtained by an emulsification by a high pressure homogenizer, using lecithin as the emulsifier, and is utilized as a preparation for a nutrient supplementation of a patient or for a parenteral administration of a lipid soluble drug.
Particularly, this compound is effective as a preparation for an intravenous injection of a lipid soluble drug which cannot be intravenously injected as an aqueous solution, and is utilized as a drug delivery system.
Recent studies of passively or actively oriented drug delivery systems with microspheres have found that, when administered intravenously, particles of 0.100 to 2.000 .mu.m are intraarterially or intraperitoneally incorporated rapidly from the blood stream by macrophages in the reticuloendothelial system, to be localized at the lysosomes of Kupffer's cells in the liver, and particles of 0.050 .mu.m pass through the liver endothelial system and are thought to be gathered probably at the tumor tissue (see: Pharmacy International 2 (3) 1984). From the above standpoint, a fat emulsion for an intravenous injection with an average particle size of 0.2 .mu.m, which is injected into the reticuloendothelial system, particularly the liver, is not satisfactory as a preparation for a parenteral administration of a lipid soluble drug, and the preparation of particles of 0.050 .mu.m or less, which can be administered parenterally, is also a very important preparation technique.
As a compound which can be parenterally administered, the fat emulsion for intravenous injection as mentioned above is known in the art, but the preparation of parenterally administrable particles of 0.050 .mu.m or less, i.e., nano-lipid spheres, in this system is very difficult, and this problem has been studied by researchers.